Try this:
grayImage = imread('cameraman.tif');
imshow(grayImage);
subplot(1, 2, 1);
imshow(grayImage);
fontSize = 20;
title('Double click inside to accept it.', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0.04, 1, 0.96]);
promptMessage = sprintf('Click and drag out a region.\nDouble click inside to quit.\nor Quit processing?');
titleBarCaption = 'Continue?';
buttonText = questdlg(promptMessage, titleBarCaption, 'Draw', 'Quit', 'Draw');
if contains(buttonText, 'Quit')
return;
end
h = imfreehand();
position = wait(h)
% Make integers
position = round(position);
% Find cropping limits.
col1 = min(position(:, 1))
col2 = max(position(:, 1))
row1 = min(position(:, 2))
row2 = max(position(:, 2))
% Do the crop
croppedImage = grayImage(row1:row2, col1:col2);
% Show the cropped image.
subplot(1, 2, 2);
imshow(croppedImage);
title('Cropped Image', 'FontSize', fontSize);
